U.S. patent number 4,949,632 [Application Number 07/277,189] was granted by the patent office on 1990-08-21 for circuit for monitoring and controlling the flow of hot air in equipment for roasting coffee, nuts and similar edible commodities.
This patent grant is currently assigned to Officine Vittoria S.p.A.. Invention is credited to Pier Cesare Camerini Porzi.
United States Patent |
4,949,632 |
Camerini Porzi |
August 21, 1990 |
Circuit for monitoring and controlling the flow of hot air in
equipment for roasting coffee, nuts and similar edible
commodities
Abstract
A circuit permits of monitoring the temperature and the color of
coffee in the drums of roasting equipment, and controlling the flow
of hot air with dampers operated in pairs by respective stepping
motors. The dampers are moved through a succession of proportioning
positions in a definite sequence of two stages; an initial,
continuous movement that approximates to the thermal transition
required, followed by a series of discrete steps producing a fine
adjustment; thus it becomes possible to ensure that the set
pre-roast and roast temperatures are reached in the drums at the
prescribed moment in time.
Inventors: |
Camerini Porzi; Pier Cesare
(Casalecchio di Reno, IT) |
Assignee: |
Officine Vittoria S.p.A.
(Bologna, IT)
|
Family
ID: |
11111527 |
Appl.
No.: |
07/277,189 |
Filed: |
November 29, 1988 |
Foreign Application Priority Data
|
|
|
|
|
Dec 4, 1987 [IT] |
|
|
3720 A/87 |
|
Current U.S.
Class: |
99/468; 34/364;
99/323.7; 99/331; 99/483 |
Current CPC
Class: |
A23N
12/12 (20130101) |
Current International
Class: |
A23N
12/00 (20060101); A23N 12/12 (20060101); A47J
031/42 (); A47J 042/52 (); F26B 003/08 (); F26B
009/08 () |
Field of
Search: |
;99/323.7,325,326,331,352,353,451,467,468,473,483,486
;34/10,57A,57R,57E ;219/400,502 ;426/233,595,467 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Simone; Timothy F.
Attorney, Agent or Firm: Balogh, Osann, Kramer, Dvorak,
Genova & Traub
Claims
What is claimed:
1. A circuit for monitoring and controlling the flow of hot air in
equipment for roasting coffee, nuts and similar edible commodities,
comprising:
first drum and a second drum, each provided with an inlet and an
outlet for the passage of hot air;
a hot air generator, in communication with both drums by way of
respective ducts connected to the inlets and outlets;
a fan unit by which the hot air is circulated through the
ducts;
monitoring means located internally of the first drum and the
second drum;
a plurality of single dampers located one in each duct adjacent the
drum inlets and outlets, operated in pairs and caused to move
between a fully open limit position and a fully closed
position;
a first controller, consisting in a processor and a comparator, one
input of which is in receipt of a set of signals reflecting the
effective temperature and color or the roasting commodity as sensed
by the monitoring means, and another input, in receipt of a set of
reference signals reflecting prescribed temperature and color
characteristics as entered at a first source processor;
drive means associated with each pair of dampers, which are
interlocked to a respective output signal emitted by the first
controller as a function of the comparison made between the
monitored signal and the reference signal relative to the
respective drum, and designed to invest the relative pair of
dampers with an opening and closing movement that consists in a
plurality of positions covered in a predetermined sequence of two
successive stages: a first continuous stage serving to produce an
initial thermal transition, and a second stage occuring as a
succession of discrete steps, which completes the overall
transition and produces a variation in temperature internally of
the drum such as will ensure that the relative temperature set
point is reached successfully, and at the prescribed moment in
time.
2. A circuit as in claim 1, wherein the single dampers of each pair
are yoked together in series and set in motion by way of a relative
mechanical linkage of conventional embodiment, in such a way that a
precise movement of the one damper is accompanied by an identical
precise movement of the other.
3. A circuit as in claim 1, further comprising a pair of dampers
located one in each outlet duct between the fan unit and the
respective outlet damper, that serve to apportion the volume of hot
air, hence the number of calories, supplied to the interior of the
two drums.
4. A circuit as in claim 1, wherein the drive means consist in
stepping motors.
5. A circuit as in claim 1, further comprising:
a vent, associated with and serving to exhaust air and gases from
the hot air generator, controlled by a relative damper;
monitoring means located internally of the hot air generator;
a second controller, consisting in a processor and a comparator,
one input of which is in receipt of a signal reflecting the
effective pressure level in the hot air generator as sensed by the
monitoring means, and another input, in receipt of a reference
signal that reflects a given pressure level entered at a second
source processor;
drive means, associated with the vent damper, that are interlocked
to an output signal emitted by the second controller as a function
of the comparison made between the monitored pressure signal and
the reference pressure signal, and designed to invest the damper
with an opening or closing movement that consists in a plurality of
positions covered in a predetermined sequence of two successive
stages: a first continuous stage serving to produce an initial
transition, and a second stage occuring as a succession of discrete
steps, which completes the transition and produces a variation in
pressure internally of the generator such as will correct any
fluctuation above or below the reference level entered at the
relative source processor.
Description
BACKGROUND OF THE INVENTION
The invention disclosed relates to a circuit for monitoring and
controlling the flow of hot air in equipment for roasting coffee,
nuts and similar edible commodities.
Conventionally, the process of roasting a given quantity of coffee
is implemented in two distinct steps. First, the coffee is
subjected to a pre-roast application of heat to lower its moisture
content, selecting temperature values such as are able to ensure a
well-balanced color of the beans; to best advantage, the
temperature adopted in pre-roasting the raw commodity will be of
the order of 150.degree.-160.degree. C.
The successive second step involves subjecting the pre-heated
product to roast temperature proper, generally
220.degree.-230.degree. C.
Needless to say, the temperatures effectively used can vary
considerably according to the different qualities of roast it is
wished to produce. The need for a batch of coffee to be roasted in
two distinct and successive steps is dictated by the fact that the
single beans will never be ripened to an identical degree. With
former methods, by which the full roast was effected in a single
operation, attempts to produce the requisite color and flavor on
particularly unripe beans led to pyrolisis in the riper beans, with
clear negative consequences for the end-product as a whole.
In a previous application for Italian patent filed under No. 3450
A/82 by the same applicant, a system is disclosed whereby the
complete coffee roasting cycle can be effected using special
equipment that comprises, amongst other components, a first and a
second drum of conventional embodiment; these drums are of
substantially equal capacity, and will be positioned to best
advantage one above the other, or at all events, at dissimilar
heights. Thus, in implementing the two steps described above, the
pre-roasted coffee beans, divested of moisture in the first drum,
can be transferred through suitable ducts into the roasting drum
proper, swiftly and at the opportune moment.
The two drums are provided with a respective inlet and outlet to
which respective hot air ducts are connected, the hot air being
produced by a suitable generator and circulated through the ducts
by a fan unit.
The volume of air caused to flow through the inlet and outlet ducts
is regulated by dampers programmed to open and shut at selected
moments that will vary according to the quantity and quality of the
blend and the duration of the roast, and can be operated by manual
or automatic means to suit requirements. Hitherto, the major
problem besetting the use of equipment of the type in question has
been one of arriving at a comprehesive and precise integration of
two parameters governing the entire roast cycle, namely: the
temperature level generated internally of the two drums, and the
time required to reach the selected level. More exactly, the
temperature rise programmed for the first drum must be produced in
the same interval of time as that programmed for the second drum,
by no means a simple matter when one considers the difference
between the two levels and the many and various thermal inertia
components traceable to the coffee itself.
Where these two temperature rises are faultlessly timed, one
achieves a continuous and regular cycle whereby one charge of full
roast is emptied from the second drum, and at the same moment,
another charge of pre-roast is transferred into the second drum
from the first. Additionally, and of great importance, the single
roast cycle effected on each charge of coffee will ensure the same
pre-roast and roast temperatures as those of the previous cycles,
such that the entire batch of coffee turned out during the full
program of cycles implemented will be uniformly roasted and
colored, giving optimum blends.
Such results have remained unobtainable thus far, in practice, by
reason of the fact that the dampers utilized to control the hot air
ducts to and from the first and second drums were adjusted by
degrees only, opening and closing in discrete steps. The roasting
cycle effected on a given quantity of coffee can now be considered
in general terms, departing for convenience's sake from the roast
proper; this occurs in the second drum, in which a temperature rise
approximately between 155.degree.-160.degree. C. and
220.degree.-230.degree. C. must be produced.
Reference may be made here to the graph of FIG. 2a, which shows the
variation in temperature T versus time t that occurs internally of
the second drum, and to that of FIG. 2b which shows the
corresponding variation in the angle .alpha. of the damper, also
versus time t.
It will be seen that the damper is fully open at the outset:
.alpha.=90.degree.. A predetermined quantity of hot air (calculated
in calories) is directed into the second drum by the fan,
sufficient to raise the temperature to an initial level T1 within a
given interval of time t1; this is indicated in FIG. 2a by a
straight line a, which reflects a substantially linear relationship
between T and t, and an angular coefficient denoted .delta..
On arrival at T1, the damper will throttle down by some 45.degree.,
whereupon the increase in temperature T is slowed up and the set
point T2 reached at t2; this further rise is reflected by the
straight line denoted b, which has an angluar coefficient of
.delta./2. The damper closes completely on arrival at T2, at which
point the temperature of the coffee is at a level of the order such
as to induce spontaneous ignition; accordingly, the temperature T
should now rise a few degrees to Ts (phantom line c), reaching a
level coinciding with the end-of-cycle mark ts on the time axis, at
which discharge is to programmed to occur, and the roast is
complete.
The part of the curve denoted c in FIG. 2a reflects the critical
point of the roast part of the cycle in the second drum, but is
indicative only, as the effective configuration depends on thermal
inertia in the coffee (moisture, oils, grease etc.).
The interval of time embraced by the part of the curve c in
question is that between the moment of the damper being shut and
the moment that the drum begins emptying. In the majority of
instances, it happens that the roast is not regulated by the flow
of hot air, and the coffee fails to arrive at the spontaneous
ignition temperature which produces the rise from set point T2 to
discharge Ts; rather, the temperature tends to fall instead of
rising (see d in FIG. 2a), and a thermoregulator with its probe
located internally of the roasting drum will cut in to re-open the
damper, say to 45.degree., for a further interval from t3 to t4,
thereby ensuring that the temperature rises to the prescribed level
Ts. The result of such an occurence is that the roast time become
extended, and the second drum is not ready to receive the
pre-roasted beans from the first drum.
Thus it happens that the pre-roast is forced to remain longer in
the first drum also (see FIG. 1a), and even in the unlikely event
that the critical stage reflected by curves c and d is avoided (the
same criteria apply as for FIG. 2a described above), the
temperature of the coffee will fall on arrival at Ts following
movement of the damper to the off position, as indicated by the
curve denoted f.
Accordingly, a thermoregulator monitoring the first drum will cut
in at t5 and re-open the damper, say to 45.degree., for a further
duration t6, thereby enabling the discharge level Ts to be
restored; the second drum will in fact have emptied by this time
and the pre-roast can be transferred.
In such a situation, the beans in the first drum are invested with
more heat than is opportune, and drop into the second drum
pre-roasted too highly; thus, the roast step implemented in the
second drum must be cut short in order to ensure that the beans
will emerge roasted and colored to the same degree as previous
charges.
With the roast now cut short, the second drum will be ready to
receive a further charge of pre-roast from the first drum before
the pre-roasting step is in fact terminated, and should this occur,
i.e. in the event that a charge of pre-roast is transferred from
the first drum to the second drum short of the temperature level
prescribed, one will be left with an under-roasted, lower
temperature product at the end of the roast cycle, and the roast
step must be prolonged in order to compensate; thus, the pre-roast
is forced once again to remain in the first drum (remembering that
the cycle is geared to the roast time-lapse in the second drum),
and there is a recurrence of all the negative factors examined
above. The end result is that one has a succession of fluctuations
in roast and pre-roast time-lapses, which become increasingly
marked, and the product necessarily suffers through the
impossiblility of obtaining a regular roast, and in particular, a
regular color, at each cycle.
More exactly, assuming the number of calories put into the drum as
par, a longer roast will allow heat to penetrate deeper into the
bean, whereas with a shorter roast, the bean will scorch on the
surface and remain raw inside.
Accordingly, the object of the invention is one of overcoming the
drawbacks described above.
SUMMARY OF THE INVENTION
The stated object is achieved, according to the present invention,
by providing the conventional equipment used to roast coffee, nuts
and similar edible commodities, with a circuit for monitoring and
controlling the flow of hot air supplied to the pre-roast and roast
drums.
In such a circuit, the two dampers serving each drum are operated
by drive means, and capable of movement between two limit
positions, fully open and fully closed, through intermediate
positions that occur in a planned sequence consisting in a first
stage of continuous movement followed by a second stage of discrete
steps, to the point of reaching the prescribed fully-open,
fully-closed or part-open position that ensures correct
conditions.
To this end, the drive means are interlocked by way of transducers
to a controller, one monitoring input of which is in receipt of
signals reflecting the effective temperature and color of the
pre-roasting and roasting charges, and another input, of signals
reflecting the prescribed temperature and color values to be
matched.
Accordingly, the output from the controller is a function of the
comparison made between its inputs, and the relative pulses can be
utilized to control the opening and closing movement of the
dampers, producing a variation in hot air flow to the drums which
will ensure, not only that the programmed temperature set point is
reached correctly, but also, that it is reached at the prescribed
moment.
The advantage of the invention is that it becomes possible to time
the temperature rise and duration of the pre-roast and roast steps
correctly, thereby eliminating the fluctuations described above and
ensuring that the end product emerges in identical condition from
each cycle.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in detail, by way of example,
with the aid of the accompanying drawings, in which:
FIG. 1 shows a schematic representation of coffee roasting
equipment incorporating the monitoring and control circuit
according to the invention;
FIGS. 1a-1b, 2a-2b are sets of graphs, relative to the pre-roast
and roast drums respectively, which illustrate the variation in
temperature T versus time t, correlated to the angle .alpha. at
which the dampers are set, likewise versus time t, obtainable with
prior art methods;
FIGS. 3a-3b are graphs relative to either durm that illustrate the
variation in temperature T versus time t, correlated to the angle
.alpha. at which the dampers are set, likewise versus time t,
obtainable with the circuit disclosed.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference in particular to FIGS. 1 and 3, a hot air monitoring
and control circuit according to the invention is designed for
application to equipment for roasting coffee, nuts and similar
edibles. A typical embodiment of such roasting equipment will
comprise, amongst other components, a first drum 1 and a second
drum 2 in which the commodity is treated; more exactly, the first
drum 1 serves to pre-roast the beans, whereas the roast proper is
effected in the second drum 2.
Each drum 1 and 2 is provided with a respective hot air inlet 1a
and 2a and outlet 1b and 2b to which respective pairs of inlet and
outlet ducts 11, 12 and 22, 33 are connected; the remaining ends of
the ducts connect directly or indirectly with a hot air generator
denoted 3. Hot air is drawn into the two drums 1 and 2 by a fan
unit 4, into which the two outlet ducts 12 and 23 are routed.
With hot air taken out of the drums 1 and 2 through the outlet
ducts 12 and 23 by the fan 4, a degree of negative pressure will be
created such as to draw further air through the inlet ducts 11 and
22 from the generator 3. Air exhausted from the fan 4 is directed
into a conventional cyclone separator 5 that serves to remove waste
matter (skins, husks) entrained from the drums, before being
returned to the generator 3 and reheated.
Each of the single inlet and outlet ducts 11, 22 and 12, 23 is
controlled by a respective damper 14, 15, 16 and 17, preferably of
butterfly flap type embodiment, located at points near to the hot
air inlets and outlets of the relativ drum 1, 2.
In a preferred embodment, each pair of dampers 14, 15 and 16, 17 is
operated by drive means consisting in a relative stepping motor 20,
21, as in FIG. 1, though the option exists of utilizing double
acting hydraulic cylinders, piloted to stroke between two limit
positions that correspond to the fully open and fully closed
positions of the dampers.
Operation of the motors 20, 21 is interlocked to a controller
denoted 22, which consists substantially in a processor and
comparator combined, one input of which is in receipt of signals
23, 24 reflecting the effective temperature and color of the beans
in the pre-roast and roast drums 1 and 2 respectively; these
monitoring signals are sensed by transducers of conventional type,
denoted 231 and 242 in FIG. 1, located internally of the relative
drums.
The remaining input of the controller 22 will be in receipt of
previously entered reference signals 25 and 26 reflecting the
temperature and color values prescribed for the contents of the two
drums 1, 2; these values are entered at a source processor 27, and
memorized as reference curves 28 and 29 that specify the
temperature-T-vs-time-t characteristic it is wished to match in
each drum 1 and 2.
The controller 22 effects a continuous comparison between the
effective temperature and color signals 23, 24, monitored at the
drums, and the reference signals 25, 26, and emits pulsed output
signals 30 and 31 that are used to pilot each motor 20 and 21 in
adjusting the position of the relative dampers 14, 15 and 16,
17.
As FIGS. 3a and 3b indicate, the opening or closing movement of the
dampers 14, 15, 16 and 17 consists in a plurality of positions
covered in a programmed sequence of two successive stages; the
first stage is continuous (straight line a, FIG. 3b), and will open
up the damper to an angle .alpha.1 that corresponds to an initial
thermal transition (straight line a, FIG. 3a) such as ensures
arrival at temperature T1 in the two drums 1 and 2; the second
stage occurs as a succession of discrete steps (b, in FIG. 3b), and
will be seen to correspond to a final thermal transition (curve b,
FIG. 3a) that takes temperature in the two drums up to the set
point Ts at the prescribed moment in time ts. Thus, variations in
temperature T within the pre-roast and roast drums are made to
occur in accordance with the reference curves 28 and 29 and time
scales entered at the source processor 27.
Controlling the roast in this way, one avoids the problems with
thermal inertia that tend to occur during the self-ignition stage
in equipment where there is no such hot air control (curves c, d
and f in FIGS. 1a and 2a); according to the invention, in fact, the
coffee is never left to continue roasting in conditions not
controlled by the flow of hot air, and the dampers will close at
the moment when discharge occurs.
It will be seeen from FIG. 1 that the dampers of each pair 14, 15
and 16, 17 are yoked together in series and set in motion by way of
a mechanical linkage 32 of conventional type, in such a way that a
precise movement of the one damper is accompanied by an identical,
equally precise movement of the other. The circuit comprises
further manually-operated dampers 33 and 34 located in the outlet
ducts 12 and 23 between the fan unit 4 and the respective outlet
damper 15 and 17; these additional dampers serve to apportion the
volume of air supplied to the drums 1 and 2, hence the number of
calories, which must differ in view of the dissimilar rises in
temperature described above, namely, from 20.degree. C. approx (or
ambient) to 155.degree.-160.degree. C. approx in the case of the
first drum 1, and from 155.degree.-160.degree. C. approx to
230.degree. C. approx in the case of the second drum 2.
Accordingly, the pre-roast and roast set points Ts will be reached
in the respective drums 1 and 2 at the prescribed moment in time,
thereby ensuring that no fluctuations occur, and that the pre-roast
and roast time-lapses are synchronized.
A single cycle consists in filling the first drum with raw coffee
beans from a charging hopper 35, the pre-roasting them to the set
temperature at the same time as the previous charge is roasting in
the second drum 2; this accomplished, the second drum discharges
its contents into a bin 36 to cool, the pre-roast is transferred
from the first drum to the second, and the cycle is repeated.
Needless to say, any given roast will be obtainable by entering the
appropriate reference curves 28 and 29 at the source processor
27.
More precisely, equipment of the type in question can be affected
by the additional drawback that pressure tends to vary from one
moment to the next internally of the circuit as moisture is
released from the beans during the roast, and as natural oils in
the coffee undergo combustion and give off gases. Such factors
combine to increase the volume of fluid internally of the drums,
and therefore to induce continual variations in pressure which are
difficult to forecast; furthermore, the rise and fall in pressure
leads to irregular operation of the hot air generator 3, which
generally will be a direct-acting type, and therefore highly
sensitive to instabilities in internal pressure conditions. With
this in mind, the pressure level internally of the generator 3 can
be guaranteed to remain between prescribed minimum and maximum
limits by inclusion of a vent 40 from which air and excess gases
can be released; the vent will also incorporate a damper, designed
to oepn in response to rising pressure, and to close when pressure
falls.
To prevent circuit pressure fluctuating above and below the
predetermined level, internally of the generator 3 in particular,
the damper controlling the vent 40 will be moved between its two
limit positions by relative drive means 41 interlocked to a second
controller 42, the comparator inputs of which are in receipt of a
monitoring signal 43, reflecting effective circuit pressure sensed
by a transducer 343 located inside the generator 3, and a selected
reference signal 44 programmed into a second source processor 45.
Thus, the controller 42 emits an output signal 46 that is a
function of the comparison made between the two input signals 43
and 44, and can be used to pilot operation of the vent damper,
positioning it such that pressure in the generator 3 is maintained
at the reference value.
The opening and closing movement of the vent damper likewise
consists in a predetermined sequence of two successive stages, the
first a continuous sweep covering the greater part of the
correction, and the second stage occurring as a series of final,
discrete steps that complete the correction and restore pressure in
the generator 3 to the level selected.
* * * * *